BUILDING SITE DEVELOPMENT AND INSTALLATIONS - Ancient Building Technology - page 79

Alexandra in his treatise on lit ing devices classii es them also in accordance with
their rig, using terms already current in the Greek building accounts and contracts.
h ese terms specify the number of legs on which the device stands, thus a one
legger, two legger, three legger or four legger. h e Greek terms are monokōlos,
dikōlos, trikōlos, tetrakōlos ( κῶλον = limb, leg, member).
h ese four dif erent types of rig are noted and described by Hero in purely for-
mal terms. Because of their transmission through Arabic MSS they have come into
modern knowledge in the same formal guise. Summary accounts of them are given
in both Martin (pp. 202-05) and Orlandos (II, pp. 36-38), accompanied in both
instances by drawings. h ese drawings are of little account since they are simply
diagrams devised in modern times to depict the text. h ey are not based on any
knowledge of classical archaeology or of building construction and therefore are
divorced from any functional analysis. In fact it is possible to recognise essential
functional distinctions and signii cance in Hero's forms from experience in using
simple lit ing devices.
First of all Hero's four forms can be divided into two groups: those which are
rigged with (guy) ropes and those which are not. h e former group comprises
the monokōlos (one legger) and the dikōlos (two legger) and the latter the trikōlos
and the tetrakōlos .
h e monokōlos is familiar as the derrick once set about the masts and samson
posts of small cargo ships. h ey were largely hand operated and eminently prac-
tical. h e single wooden jib carried a pulley attachment at the peak and it could
be inclined or swivelled around horizontally by hand held ropes, so that it could
pick up and discharge loads anywhere within its radius. h e critical requirement
was a swivel joint of some sort at its base. Its operation was facilitated by being
moored to a strong upright, but this was not absolutely necessary.
h e advantages of mobility inherent in the monokōlos are commented on in
ancient references to it; but the contrivance which secures this, the swivel joint,
is not—and it does not appear in any representation. Presumably it was some
sort of shallow stone lined socket let into the ground. h e operational virtue of
the monokōlos was apparent in the nautical derrick of former times. It could
pick up modest loads from anywhere and deliver them anywhere within the radius
of its jib. It was not intended for raising heavy loads to a considerable height.
It may well have been convenient in the construction of tholoi and of small
ashlar domes.
Within the same genre as the monokōlos was the dikōlos . h e dif erence was that
the kōlon here was not of a simple pole, but of two legs trussed together forming a
stronger jib. h e jib could be raised and lowered by ropes (themselves operated by
pulleys), thus making possible some horizontal displacement of the load, but only
in a single linear sense. In the nature of things the device could not be swivelled

Pulley
rigs

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